The present invention relates to improvements in fluid sample flow cells and more particularly to a high pressure fluid sample flow cell with a circumferential window edge seal.
Fluid sample flow cells commonly comprise a metal or plastic cell body having a fluid passageway therethrough. A fluid inlet connected to one end of the passageway flows a sample fluid with analytes to be detected from a sample source, such as an LC column. The sample fluid flows along the passageway to exit at an outlet from an opposite end of the passageway. While the fluid is flowing along the passageway, it is exposed to a light beam transmitted from a light source to a light detector through windows at opposite ends or sides of the passageway. Variations in light absorbance monitored at the detector are utilized to identify and quantify the analytes in the fluid sample.
In such flow cells it is of course important that fluid not leak from the cell body and that the connections between the windows and the cell body be fluid tight. In the past, such fluid tight seals have been defined by window face sealing means such as annular plastic gasket or O-ring seals. To create a window face seal the annular seal has been placed on a flat face of the window and the window and seal forced tightly together as by clamps, clips and the like. U.S. Pat. Nos. 3,515,491; 3,647,304 and 4,374,620 describe such window face seals.
In high pressure flow systems having an internal fluid pressure of 1000 psi and more, the challenges relative to fluid tight seals are much more severe than in low pressure systems. Yet today, window seals in such high pressure systems still utilize the standard face seal approach only with greater and greater forces being developed between the annular seals and the face surfaces of the windows. In practice, this has resulted in undesired fracturing and cracking of cell windows and rapid deterioration of over-stressed seals.